Memory modules such as dual-inline memory modules (DIMMs) are widely used in a variety of systems such as personal computers (PCs). Since profit margins for memory module manufactures are low, manufacturing costs must be reduced. Testing costs can be reduced by testing memory modules on a low-cost modified PC motherboard rather than an expensive electronic-component tester.
An extender card can be inserted into a memory module socket on a standard PC motherboard. This extender card has another memory module socket mounted on a top edge, while the bottom edge is inserted into the motherboard's memory module socket. The extender card effectively raises the location of the open memory module socket up off the surface of the motherboard, allowing easier access to the socket.
FIG. 1 shows a memory module extender card between a PC motherboard and a memory module being tested by the motherboard. Motherboard 26 has components 28 and memory module socket 18 mounted on a component side. Many components such as integrated circuit (IC) chips, resistors, capacitors, fans, connectors, and plugs can be mounted, and many motherboards have two or four memory module sockets 18.
Normally, memory module 10 is inserted directly in memory module socket 18 so that metal contacts 14 mate with metal contacts inside memory module socket 18. However, cables and components 28 may crowd around memory module socket 18, making it difficult to insert memory module 10. While module insertion is performed rarely in an end-user PC, when motherboard 26 is used to test memory modules, such restricted access is problematic.
Easier insertion of memory module 10 during such testing is provided by extender card 12. Metal contacts 24 on the bottom edge of extender card 12 are inserted into memory module socket 18. Metal traces on extender card 12 connect signals from metal contacts 24 to corresponding contacts inside extender socket 20.
During testing, memory module 10 is inserted into extender socket 20 on extender card 12. Since extender socket 20 is raised above memory module socket 18 on motherboard 26, socket access, and insertion and removal of memory module 10 are facilitated.
Some memory module sockets feature retention devices to lock the memory module into the socket. This prevents accidental loosening of the connection, or even loss of the memory module. For example, clip 22 on extender socket 20 can be moved inward to clip into notch 16 on memory module 10 after memory module 10 is fully inserted. Memory module socket 18 on motherboard 26 may also have such clips 22 for retention.
FIGS. 2A–B show operation of a retention clip on a memory module socket. Retention clip 22 is in the open position, moved outward and away from extender socket 20. Memory module 10 is inserted into extender socket 20 with retention clip 22 open, as shown in FIG. 2A. Notch 16 is lined up with retention clip 22 when memory module 10 is fully inserted into extender socket 20.
In FIG. 2B, retention clip 22 is moved inward, causing a knob on retention clip 22 to engage inside notch 16 on memory module 10. The knob on retention clip 22 engaging notch 16 prevents accidental removal of memory module 10.
However, memory module 10 must be fully inserted into extender socket 20 before retention clip 22 can be clipped into notch 16. A fair amount of force needs to be applied to memory module 10 by the user to insert memory module 10 fully into extender socket 20.
While insertion force may be significant, the force necessary for removal may be more difficult to apply, since it is a pulling rather than a pushing force. Some memory module sockets are equipped with ejectors to initially remove or start removal of an inserted memory module.
FIGS. 3A–B show operation of an ejector in a memory module socket. An extension of retention clip 22 may be formed below the fulcrum or pivot point of retention clip 22. This extension is normally hidden from view, inside extender socket 20. The extension of retention clip 22 is extension ejector 30 in FIGS. 3A–B.
When memory module 10 is fully inserted into extender socket 20, and retention clip 22 is clipped into notch 16, as shown in FIG. 3A, extension ejector 30 is in its lowest position, below memory module 10. The bottom (connector) edge of memory module 10 may touch a foot portion on the end of extension ejector 30.
To begin removal of memory module 10, a user pulls outward retention clip 22, as shown in FIG. 3B. As retention clip 22 is moved outward, extension ejector 30 pivots upward inside extender socket 20. The foot of extension ejector 30 pushes upward against the bottom edge of memory module 10, forcing memory module 10 upward out of extender socket 20. Typically extension ejector 30 only moves memory module 10 upward a slight distance, and the user finished removal of memory module 10 by pulling upward on it.
While such retention clips and extender cards are useful, a strong force is often needed to insert the memory module. When a technician or test operator has to manually force memory modules into test sockets, such forces can produce repetitive stress injuries or may damage the memory module, extender card, or motherboard tester. Often memory modules must be replaced every 2–5 minutes in a test or lab environment.
What is desired is a memory module extender socket with an insertion aid. A memory module socket that uses leverage to increase the user's force on the memory module during insertion is desirable. A test apparatus with extender cards and leveraged insertion of memory modules into sockets is desirable.